1. Field of the Invention
The present invention relates generally to the treatment of tear fluid deficiencies in the eye and, more particularly, to punctum plugs and methods of punctal occlusion for deterring the drainage of tear fluid from the eye.
2. Brief Discussion of the Related Art
Normally the eye is protected and lubricated by a film of naturally produced tear fluid spread over the corneal and conjunctival epithelia through blinking. Various problems may arise in the eye, however, where the quantity of tear fluid in the eye is deficient, and such problems may be referred to generally as dry eye syndrome. Tear fluid deficiencies are oftentimes chronic and may result from inadequate tear fluid production and/or drainage of too much tear fluid from the eye through the lacrimal drainage system of the eye. Various conditions may cause and/or aggravate tear fluid deficiencies including disease, inflammation, congenital defects, side effects of over-the-counter and prescription drugs, environmental irritants or effects, atrophy, aging, eye strain, and procedures performed on the eye such as Lasik and cataract procedures.
Dry eye syndrome is increasing in prevalence and it is estimated that up to 40% of the U.S. population suffers from dry eye syndrome to some extent. Dry eye syndrome may manifest as various ophthalmic ailments including itchy, gritty, sticky and/or burning sensations, conjunctivitis, blepharitis, contact lens problems, corneal erosion, incipient corneal graft rejection, recurrent chalzion, pinguecula, corneal ulcers and acute lid abscesses. Sinus ailments, hay fevers, colds and other recurrent infections have been attributed to dry eye syndrome.
One common treatment for dry eye syndrome involves the introduction of artificial tear fluid into the eye. The benefits derived from artificial tear fluids are limited and are usually of short duration. In some users, artificial tear fluids have caused toxic reactions. Other drawbacks of artificial tear fluids include possible blurred vision and unsightly deposits on the eyelids.
Mechanical devices such as punctum plugs which block or occlude the puncta to deter drainage of tear fluid from the eye have been proposed and are represented by U.S. Pat. Nos. 3,949,750 and 5,283,063 to Freeman, U.S. Pat. No. 4,915,684 to MacKeen et al, U.S. Pat. No. 4,959,048 to Seder et al, U.S. Pat. Nos. 5,723,005, 6,149,684 and 6,290,684 B1 to Herrick, U.S. Pat. No. 5,417,651 to Guena et al, U.S. Pat. No. 5,423,777 to Tajiri et al, U.S. Pat. Nos. 5,741,292 and 6,027,470 to Mendius, U.S. Pat. No. 5,830,171 to Wallace, U.S. Pat. Nos. 6,016,806 and 6,041,785 to Webb, U.S. Pat. No. 6,234,175 B1 to Zhou et al, U.S. Pat. No. 6,306,114 B1 to Freeman et al, and U.S. Pat. No. 6,344,047 B1 to Price et al.
Punctum plugs typically include a proximal head, a distal tip and a shaft connecting the proximal head and the distal tip. The shaft is often smaller in cross-sectional size than the proximal head and the distal tip. A punctum plug is usually inserted, distal tip first, in a punctal opening of the punctum and is advanced distally in the punctum until the proximal head is seated on the punctal opening. The proximal head is normally larger than the punctal opening such that the proximal head does not pass through the punctal opening and remains exposed in the eye. The distal tip typically has a cross-sectional size to fill the canalicular canal which is in communication with the punctal opening and to anchor the punctum plug in place. Usually the proximal head overlaps and is in abutment with a rim of anatomical tissue circumscribing the punctal opening. The blockage or occlusion presented by the punctum plug deters tear fluid from draining from the eye through the punctal opening and the corresponding canalicular canal from which tear fluid would otherwise drain into the lacrimal sac and through the nasolacrimal duct into the nasal cavity.
Typically, punctum plugs are implanted in the eye using insertion tools, and punctum plugs having axial passages for releasably engaging the insertion tools to facilitate or guide implantation have been proposed as represented by U.S. Pat. No. 3,949,750 to Freeman, U.S. Pat. No. 4,915,684 to MacKeen et al, U.S. Pat. No. 5,171,270 to Herrick, U.S. Pat. Nos. 5,283,063 and 5,334,137 to Freeman, U.S. Pat. No. 5,423,777 to Tajiri et al, U.S. Pat. No. 5,723,005 to Herrick, U.S. Pat. Nos. 5,741,292 and 6,027,470 to Mendius, U.S. Pat. No. 5,830,171 to Wallace, U.S. Pat. No. 6,016,806 to Webb, U.S. Pat. No. 6,149,684 to Herrick, U.S. Pat. No. 6,306,114 B1 to Freeman et al, and U.S. Pat. No. 6,344,047 B1 to Price et al, and U.S. Pat. No. 6,527,780 B1 to Wallace et al.
The proximal heads of the punctum plugs remaining exposed in the eye may be engaged with the insertion tools or other instruments by which the punctum plugs may be withdrawn from the punctal openings for removal from the eye. The proximal heads thusly enhance the ease with which punctum plugs may be implanted in and removed from the eye and enable greater patient comfort and safety during implantation and removal. Furthermore, the proximal heads facilitate proper positioning of the punctum plugs in the eye and inhibit displacement of the punctum plugs by preventing the punctum plugs from being advanced too far in the puncta. Disadvantageously, however, the exposed proximal heads of conventional punctum plugs may cause corneal irritation and/or lid sensation in patients, resulting in discomfort and/or intolerance for many patients. Attempts have been made to avoid corneal irritation and/or lid sensation by reducing the profile or thickness of the proximal heads; however, structural strength and integrity are thereby sacrificed. The axial passages of conventional punctum plugs are not useful to retain tear fluid on the proximal heads of the punctum plugs for exposure in the eye due to the axial passages being of appreciable length.
Intracanalicular implants have been proposed which are disposed entirely within the canalicular canal without exposure or protrusion thereof in the eye, and such implants are illustrated by U.S. Pat. Nos. 4,660,546, 5,049,142 and 5,053,030 to Herrick et al and U.S. Pat. Nos. 5,163,959 and 5,171,270 to Herrick. Intracanalicular implants which are disposed entirely within the canalicular canal are more difficult to implant and remove and are more likely to be implanted improperly or to become displaced in the canalicular canal.
Conventional punctum plugs may be made available in different sizes corresponding to anatomical puncta and canaliculi of different cross-sectional sizes. Since the anatomical puncta and canaliculi are of microscopic size, punctum plugs are also of microscopic size. Consequently, it is very difficult to distinguish between different size punctum plugs, and it is particularly difficult to visually ascertain the size of a punctum plug while implanted in the eye.
Accordingly, there is a need for a punctum plug having a proximal head or cap which remains exposed in the eye following implantation of the punctum plug while reducing the potential for corneal irritation and/or lid sensation from the exposed cap. A need exists for a punctum plug having a cap which retains tear fluid thereon for wetting the cornea when the cap is exposed in the eye after implantation of the punctum plug in the eye. There is also a need for a punctum plug in which tear fluid is collected in and adheres to a cap of the punctum plug via surface tension of the tear fluid in one or more shallow recesses of the cap. Another need exists for a punctum plug that enables size identification of the punctum plug to be accomplished through visualization of a cap of the punctum plug while the punctum plug is or is not implanted in the eye.